Method of producing artificial yarn



April 194& E. A. TIPPETT'S METHOD OF PRODUCING ARTIFICIAL YARN Filed Aug. 19, 1943 3 Sheets-Sheet 1 IN V EN TOR [MERJ oA/A. 77/671'5 A 7' TORNEX April 20, 1948. p 5 2,439,829

METHOD OF PRODUCING ARTIFICIAL YARN Filed Aug. 19, 1943 3 Sheets-Sheet 2 IN V EN TOR EMERJONA. TIPPETTJ ATTORNEY April 20, 1948.

E. A. TIPPETTS 2,439,829

METHOD OF PRODUCING ARTIFICIAL YARN Filed Aug. 19, 1943 3 Sheets-Sheet 3 /Zmu/ A TTOR/VEY Patented Apr. 20, 1948 METHOD OF PRODUCING ARTIFICIAL YARN Emerson A. Tippetts, Richmond, Va., asslgnor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application August 19. 1943, serial No. 499,162 7 Claims. (Cl. 18-8) This invention relates to the manufacture of high tenacity regenerated cellulose yarn from viscose by the hot dip method. More particularly, this invention relates to a method for use in the hot dip method to produce high tenacity regenerated cellulose yarn of substantially uniform physical characteristics.

United States Patents No. 1,901,007 of March 14, 1933, and No. 1,996,989 of April 9, 1935, disclose procedures for producing viscose rayon of improved tenacity by passing the c'oagulated partially' regenerated filaments through a hot aqueous bath heated to 70 C. to 100 C. and, while the filaments are in contact with such hot aqueous bath, subjecting them to substantal tension and/or stretching. In each of the procedures disclosed in the aforementioned patents, the amount of swelling or plasticizing of the yarn by the hot water treatment was not readily controllable and the application of stretch over substantial length of the yarn did not given consistent reproducible results so that a product of uniform characteristics could be obtained.

United States Patent No. 2,248,862 of July 8, 1941, discloses a hot bath stretching arrangement wherein the first feed wheel is partially immersed in the hot bath and whereby the hot bath is applied only at the bottom of the feed wheel. The

application of the hot bath to the first (feed wheel.

only at the bottom thereof limits the take-ofl point of the yarn to the side of the feed wheel and at a point not greater than 60 from the point where the feed wheel contacts the hot bath if the thread is to be at the maximum temperature (and this is necessary for optimum results) at the time of stretching. If the thread were taken off at some other point greater than 60 from the point of application of the hot bath, such as from the top of the first feed wheel in its passage to the second ifeed wheel, the temperature of the thread at the time of stretching would be less than the temperature of the bath due to cooling by evaporation from the feed wheel. Additionally, such arrangement is objectionable in that it prevents the imposition of themaximum possible tension, such as of the order of 1 I inability of the arrangement in said Patent No.

2,248,862 to impose these extremely high spinning. tensions on the freshly formed yarn is apparently due to the ciact that stationary yarn directional guides are used and the frictional resistance to the travel of the yarn makes it necessary to spin at lower tensions than would be possible if the yarn came in contact with'substantially'no frictional resistance. Further, the application of hot bath to the yarn passing around the roller, as disclosed in said Patent No. 2,248,862, is not suited to the optimum control of stretching as will be more fully explained hereinafter.-

Slippage of the freshly formed yarn on the feed wheels when yarn was being spun by the bucket spinning process was a major problem some years ago. The use of double wraps around the feed Wheel and especially the use 01 a freely rotatable snubber guide roller, such as shown in United States Patent No. 1,977,611, was decidedly helpful in the development of yarn of more uniform properties. However, in the. spinning of large denier yarns, such as 1100 denier, under high tension, and especially when the yarn is, treated with a hotaqueous bath and stretched a substantial amount, a small number of the filaments are commonly broken. The hot bath does not act instantaneously on all the filaments comprising the bundle and; as soon as most of the filaments become plasticized, they stretch, releasing a large part of their load to the less plasticized filaments which bear or try to hear an unproportiorially large load, and finally break. These broken filaments most frequently wrap around the snubber guide roller, continue to build up, and often cause other filaments to break, until the entire bundlebreaks or until the wrap becomes so large as to prevent normal operation gram per denier, between the two positively of the roller.

In addition, the advent of much higher spinning tensions (of the order of 1 gram per denier) made necessary, in order to maintain a high degree of uniformity, a plurality of complete wraps around the feed wheel and two or more wraps around the snubber roller guide. While slippage of the yarn on the stretching wheel was thus avoided, increased roller wraps were a barrier against any practical application. It is, of course, apparent that in spinning at tensions well below the yarn breakingtension many of these difllcu lties never arise. Nevertheless, when spin.-

ning at speeds 25% to 50% higher than commonly used and at maximum tensions on the filament bundle within to of the break-.

ing tension, what would normally be considered extremely minor irregularities become of extreme importance and the procurement of optimum benefits from this extremely high tension spinning are vitally dependent on every minute refinement.

It is an object of this invention to provide an improved process for the impregnation of freshly spun viscose rayon yarn with a hot aqueous liquid and stretching the same. Another object of this invention is to stretch the freshly spun viscose rayon yarn impregnated with a hot aqueous liquid between two feed wheels. Other objects will be apparent from the description hereinafter set forth.

The objects of the invention are generally accomplished by stretching freshly spun viscose rayon yarn between two positively driven feed wheels, the yarn passing one or more times around the first feed wheel and a plurality of times around the second feed wheel. While the yarn is on the first feed wheel, it is uniformly impregnated with a hot aqueous liquid. the peripheral speeds of the feed wheels are such as to impose in the yarn a total tension of the order of 1 gram per denier. As will become apparent hereinafter, the stretch is confined within a short distance in the path of travel of the yarn (as it comes onto the first feed wheel and as it leaves said feed wheel) and at a time when the yarn is uniformly impregnated with the hot aqueous bath.

This invention is directed to improvements in the process involving hot aqueous bath stretching wherein the bath may be water, acidulated water, or a viscose regenerating bath of the same or different composition as that into which the viscose is initially spun. It has been found that optimum results are obtained by applying to the yarn to be stretched a bath heated to a temperature of about 90 C.- to 95 C. so that stretching will take place in yarn that is not below 85 C. at the region and time of stretching, although excellent results can often be obtained by impregnating the yarn to be stretched at much lower temperatures, such as at 75 C. or thereabouts. v

For convenience, the invention will be described in connection with the method and apparatus forming the subject-matter of application Serial No. 673,446.

The details of the invention will become more apparent by reference to the accompanying drawings when taken inconnection with the following detailed description,

In the drawings,

Figure 1 is a perspective view, partly in section, showing an apparatus suitable for carrying out the invention;

Figure 2 is a front elevation of the first stretching wheel and the snubber roller cooperating therewith, and also showing the zone of hot bath application;

Figure 3 is a side elevation of the set-up shown in Figure 2 Figure 4 is an enlarged front elevation, partly in section, oi the means for applying the hot aqueous bath;

Figure 5 is a top plan view, broken away for clarity, showing the arrangement of the snubber roller with respect to the feed wheel;

Figure 6 is a modified form' of snubber roller suitable for use when two passes of the yarn are made about the snubber roller;

Figure 'l is a section of another modified form of snubber roller suitable for use when two 4 passes of yarn are made about the snubber roller; and

Figure 8 is a top view, partly broken away for clarity, showing the arrangement of the snubber roller with respect to the feed wheel when two passes of the yarn are made about the snubber roller.

Referring now to the drawings wherein like reference numerals designate like parts, the reference numeral i0 designates a multi-hole spinneret through which the viscose solution, sup plied thereto through a conduit I2, is extruded into a spinning bath l4 contained in a trough I6. The filaments l8 extruded within the bath through the spinneret Ill are passed around guides 23, 22, 24, 26 and 28 positioned beneath the level of the bath. The guide 28 is designed to impose a tension on the yarn and may be of the type shown in United States Patent No. 2,083,251. The yarn 30 is withdrawn from the bath l4 by a positively driven feed wheel 32 and passed once around said feed wheel 32. In its passage over and around the feed wheel 32, the yarnis passed under a freely rotatable snubber roller 34. From the wheel 32, the yarn is passed over and a plurality of times around a second positively driven feed wheel 36. The yarn 30, in its passage around the feed wheel 36, also passes under a freely rotatable snubber roller 38. The feed wheels 32 and 38 are mounted on shafts 40 and 42, which are driven by means (not shown) at such rates that the peripheral speed of the wheel 36 is greater than the peripheral speed of the wheel 32 whereby the yarn between said wheels is stretched. After leaving the feed wheel 36, the yarn is collected in a rotating bucket 44 into which it is guided by a reciprocating funnel 46.

While the yarn 30 is on the first feed wheel 32, it;3 is impregnated with a jet of hot aqueous bath The feed wheel 32 is provided at the rear thereof with an upwardly inclined (slinger ring) flange 54, from which the hot bath liquid applied to the feed wheel is discharged into a collecting shroud 56 from which it is removed by a conduit 58. In order that the bath be discharged from the feed wheel 32 only at the flange 54, the jet of hot liquid 50 is applied to the upper portion of the feed wheel 32 within the range of 120, as shown in Figure 2, and the thread-contacting portion 59 of the feed wheel is constructed with a slight taper, as indicated by the reference character A in Figure 3, to insure that centrifugal force will drive the liquid from the thread-contacting portion 59 of the feed wheel 32 to the point of the flange 54 before discharging it from the wheel. While this taper A may be no more than'1, preferably it is greater than 3, but in no case more than 6 or 8.

' The region of application of the jet 5|] will V vary with the contour of the feed wheel 32, the

peripheral speed and radius thereof. When the yarn 30 leaves the wheel 32 at the top, as indicated in Figure 2 by the reference character T, the jet 50 is located preferably at an angle of 10 or anywhere within the 75 angle, designated as C in Figure 2. when the yarn leaves the wheel 32 from the side, referred to as altemate route of thread and designated by the reference character S, the jet 50 is directed onto the wheel 32, preferably at the top center or anywhere within the 45 angle marked D. In all cases, the jet of hot bath liquor 50 is applied to the yarn within a zone of an angle of about from the point the yarn leaves the wheel, and it is preferably also so directed as to have a component of its vglocity in the direction of rotation of the wheel 3 Part of the stretching of the yarn 30 takes place over the surface 69 of the feed wheel 32 just before the yarn loses contact with the wheel, resulting in slippage of the yarn on the wheel. It is, therefore, important that the yarn be in the most plastic condition possible to keep this slippage at a minimum, and. to provide plenty of lubrication by means of a liquid so that this slippage willnot damage the yarn. Some slippage also occurs in the region where the yarn 30 first contacts the wheel 32, since the surface 59 of the wheel is wet with the hot treating liquor. The tension device 28 located-in the spinning bath I4 serves as a retarding force on the yarn, which stretches the partially heated yarn on the feed wheel before sumcient contact of the surface is present between the yarn and the feed wheel to prevent slippage. It is, therefore, very important that the point of application of the hot bath jet 50 be uniform on the wheel 32 from position to position and that the desired point of application of the jet be determined to control the amount of preliminary stretch to give the best results. By this process, the yarn that is stretched in the primary bath is then given a preliminary small amount of stretching before becoming positively engaged on the feed wheel and is then brought to a temperature of about 90 C. just prior to its final stretching between the feed wheels. The optimum location of the Jet will vary somewhat, as previously indicated, depending on the peripheral speed and radius of the feed wheel.

Several factors are considered in the construc-' tion of the jet and the exact angle of impingement of the bath on the wheel. The temperature of the hot aqueous bath liquid drops from the time it first contacts, the yarn until it is removed from the wheel. The absolute temperature drop across the wheel will be determined by" the absolute magnitude of flow of the hot bath. Since it is desired to keep the temperature drop at a minimum, fairly large flows of hot bath are used. In the form shown in the drawings. the jet 50 is obtained through the use of a pipe 62, which is provided with an orifice 64 at a suflicient distance from the mouth of the pipe to permit the jet 50 to be supplied in a smooth large fiow and to prevent splashing of the jet when it impinges on the wheel 32. The pipe 62 is secured to the shroud, as shown in Figures 2 and 3, and the hot bath liquid is supplied at a constant pressure to the top thereof from a source (not shown).

As previously mentioned, the jet is directed so as to have some component of its velocity in the direction of rotation of the wheel. The yarn lies on the feed wheel in the form of a ribbon, due to the extremely high tension imposed on the yarn and its normal tendency to hug the wheel, and the direction of the jet upon this ribbon of yarn with positive force achieves more rapid penetration of heating liquor into the yarn.

It is desirable to eliminate all sharp comers or edges from the feed wheel 32, thereby eliminating points and edges from which the bath may be discharged from the feed wheel rather than be pumped to the slinger ring flange 54 where it is discharged into the shroud'56. The proper contour of the feed wheel 32 is also partially determined by the angle between the plane of re.- tation of the feed wheel 32 and the horizontal. If the thread-contacting surface 59 slopes too steeply from the flange 54 to the front of the feed wheel 32, gravity partially overcomes centrifugal force and the treating liquor is discharged from the front of the feed wheel. The flow of hot bath along the upper surface of the wheel is aided by tilting the plane of rotation of the wheel from the vertical by an amount approximately equal to the degree of taper of the feed wheel.

In the set-up shown in Figures 1, and 3, the

yarn 30 is given one pass under the snubber roller 34. Insuch a set-up, the snubber roller 34 may be like that described in United States Patent No. 1,977,611. A'sdes'cribed in said patent, the snubber roller 34 has a frusto-conicalthreadcontacting portion 66 and an upwardly inclined flange 68 at the rear thereof. The snubber roller 34 is freely rotatable .on a stud 10,. and the flange 68 is positioned within a shroud 12. A pipe 14 conducts any liquor, which passes from the snubber roller 34 to. the shroud'12, to the conduit 58.

As disclosed in application Serial No. 673,446, the snubber roller 34 must be positioned and located as hereinafter described. As shown in Figures 3 and 5, the snubber roller'34 is mounted in front of the verticalline extending down from the tangent point of first contact of the thread with the feed wheel 'by-a smallamount, and the axis of the. snubber 'guideQis. horizontally rotated out of the vertical plane-=passing through the axis of the feed wheel .by. fa small angle of about 6 or 8. I

By locating the snubber guide 34 in this manner, the yarn 30 oming down from the feed wheel 32 first contacts the flange of the snubber 34 and, due to the askew position thereof, rolls down the flange onto the (less'tapered) frusto-conical body 66. Because the yarn rolls on itself 'in coming onto the snubber roller 34, it develops temporarily a certain amount of twist. The twist actually takes place between the point at which the yarn leaves the. feed wheel 32 and the contact point with the snubber guide roller 34, so that the yarn contacting the snubber roller 34 is well bundled and broken filaments are not picked up and wrapped around the snubber roller 34 but are carried along as part of the continuous filament bundle. When the yarn leaves the snubber roller 34 and travels to the feed wheel 32, the twist is removed. However, due to the brief existence of the twist, the many filaments comprising the yarn are more closely bundled together than they would be otherwise, and the yarn is prevented from being spread out as a wide ribbon on the snubber roller 34. As previously stated, due to the high tension imparted in the thread, it is appreciably flattened as a ribbon on the wheel 32, but the filaments are still all sufliciently united that, when substantial stretching of the yarn takes place, each filament more uniformly assumes its share of the load.

The arrangement shown in Figures 2, 3 and 5 illustrates one wrap around the snubber roller, which is entirely satisfactory when the tension differential between the oncoming yarn and'the yarn leaving is not too great. When this differential is large, then the yarn should be given two or more passes around the feed wheel and snubber roller.

.If two passes of the yarn are to be made about the snubber guide roller, snubber guide rollers of the type shown in Figures 6 and '7 may be used, and the twist will be imparted to the yarn in its two successive passes therearound.

Referring now to Figure 6, the reference numeral ll designates a one-piece snubber roller rected first onto the flange 86, from which it is rolled onto the thread-contacting surface I: to impart the temporary twist. In its second pass, the yarn 30 is fed onto the flange 88 and is rolled onto the thread-contacting surface Bl whereby the temporary twist is imparted to the thread. when snubber roller 80 is any filament wraps which occur between the flanges 88 and 86 can be removed only with some difliculty.

The modified snubber roller designed to take two passes of the yarn therearound and to satisfactorily displace the yarn and impart the twist thereto, shown in Figure '7, comprises two elements SI and 92 which are independently and freely rotatable on a stub shaft 94, one end of which is fixedly mounted in a shroud 95. The

rotatable elements 90 and 92 are held on the shaft by means of a press-tit washer 98. The element 90 has a substantially cylindrical body I02 and an inclined flange II at the rear thereof. The element Q2 also has a substantially cylindrical body I06 and an inclined flange I" which terminates in a small cylindrical flange Ill. The rotatable element 92 is smaller than the element 96 and it is so mounted that the substantially cylindrical body I02 of the element SI overlaps and is spaced from the flange ll of the element 92. As is shown in Figure 7, the element 92 is provided on the rear end thereof with a boss 2 which is positioned in a recess Ill and on the front face of the element Ill. While the liquid discharged from the element 82 generally flows over the rounded shoulder of the element 90, due to the action of centrifugal force a certain amount may be discharged into the recess H4, in which case it is conducted by means of ducts II! to a passage 8, from which it is removed by the conduits I20. The liquid from the element SI is discharged in the passage Ill. In operation, this snubber roller is positioned in the same askew manner beneath the feed wheel 32 as the snubber roller 34, and as diagrammatically shown in Figure 8.

In operation, the yarn 30, as it comes from the feed wheel, is led onto the flange ill, from which it rolls onto the thread-contacting cylindrical surface I02 and whereby the temporary twist is imparted to the yarn. In its second passage, the yarn 3B is led onto the flange I", from which it rolls onto the thread-contacting cylindrical surface it whereby the temporary twist is imparted. By having both elements 90 and $2 independently rotatable, each of them seeks its own speed of rotation, when driven by the yarn pass In this way, any chance of.

ing therearound. frictional rubbing of the yarn on the surface is avoided because only one path of the yarn is in contact with each independent rotatable element of the guide. The slope of the flanges I and III is preferably about 40 to 50 with respect to the axis of rotation.

If more than two passes of yarn around the feed wheel are desired, the snubber roller hereinbefore described may be substituted by snubher rollers having three or more independently rotatable elements of the type shown in Figure 7, or, when a single roller is used, three or more 8. flanges and thread-contacting surfaces of the type shown in Figure 6.

The snubber roller 38 may be of any of the types herein described, depending of course on the number of passes the yarn makes therearound. Because of the high tension on the oncoming side and the relatively low tension on the yarn leaving the second wheel 36, it is preferred and more generally needed to use snubber rollers 10 of the type shown in Figures 6 and '1 wherein a double pass of the yarn about the snubber roller is obtained.

The feed wheels and the snubber guides herein described are constructed of such surface material that sulfur and sludge from the spinning bath will not adhere in the yarn path, forming ridges from which the hot liquidwillbedischarged without flowing to the flange. A glass surface has given satisfactory results.

Instead of collecting the yarn in a bucket, it

26 Example A viscose solution containing 1% cellulose, 6% H8011 ripened to a sodium chloride salt index of 5.2 is spun into a primary acid-salt bath and m then is stretched 20% between two feed wheels.

the hot bath consisting of 95 (3. water acidulated by the primary bath carried along with the yarn being applied to the yarn on the flrst of the two wheels substantially as shown in Figure 1. The

yarn, which. will be finished in the form of 1100 denier, 480 filaments. comes from the primary bath \mder a tension of 660 grams and the 20% stretch applies additional tension, so that between the two feed wheels the tension is equal to 1060 grams. The yarn is collected in a centrifugal spinning bucket under an average tension of about 15 grams (measured between the second feed wheel and the bucket funnel). and in view of this great tension differential three passes of yam are made over the second feed wheel, necessitating a double pass of yarn under the snubber roller guide, although but a single pass is needed under the snubber roller guide associated with the first of the stretching feed wheels since the tension differential here is relatively small,

During 5 hours of spinning, using the double roller guide shown in Figure 'I under the second feed wheel and so positioned that a temporary twist was produced in the yarn with each pass thereto, not a single wrap was formed and the yarn producedwas of uniform high quality with the desired high tenacity. However, when this double roller snubber guide was replaced with a one-piece cylindrical roller under which the yarn so passed without the benefit of temporary twist being applied thereto, eight wraps were formed during a 5 hour period, of which two wraps built up so large by entanglement of other filaments that the yarn was broken.

This invention enables the production of yarn of substantially uniform physical properties having a desirably high elongation as well asghigh tenacity, good knot strength, and excellent fatigue value. Such yarn is eminently suited 7 for the manufacture of cord for use in the reinto tion permits the production of yarns of higher average dry tenacities than have been possible heretofore by the hot bath spinning method and greatly reduces spinning difficulties.

The snubber rollers, the method of imparting the twist and the removal thereof, and the combination method wherein the yarn is both treated with a jet of hot aqueous liquid on the first feed wheel and twisted and untwisted, form the subject-matter of divisional application Serial No.

Since it is obvious that many changes *and modifications can be made in the above-described details without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited thereto except as set forth in the appended claims.

I claim:

1. In the process of stretching viscose yarn between two spaced positfvely driven feed wheels, the step which comprises applying a jet of hot aqueous liquid to the yarn on the first feed wheel and while the yarn is within a zone of 90 from the point it leaves said feed wheel to pass to the second feed wheel, the temperature of said aqueous liquid being such as to heat said yarn to a temperature of at least 75 C., said jet being so directed as to have a component of its velocity in the direction of rotation of said first feed wheel.

2. In the process of stretching viscose yarn between two spaced positively driven feed wheels,

the steps which comprise leading the yarn from the top of the first wheel to the second wheel, and applying a jet of hot aqueous liquid to the yarn while it is on the first wheel and within a zone of 75 from the point it leaves said first wheel to pass to said second wheel, the temperature of said aqueous liquid being such as to heat said yarn to a temperature of at least 75 C., said jet being so directed as to have a component of its velocity in the direction of rotation of said first feed wheel.

3. In the process of stretching viscose yarn between two spaced positively driven feed wheels, the steps which comprise leading the yarn from the downrunning side of the first wheel to the second wheel, and applying a jet of hot aqueous uid to the yarn while it is on the first wheel and within a zone of 45 to 90 from the point it leaves said first wheel to pass to the second wheel, the temperature of said aqueous liquid being such as to heat said yarn to a temperature of at least 75 C., said jet beingv so directed as to have a component of its velocity in the direction of rotation of said first feed wheel.

4. A method as set forth in claim 1, wherein the temperature of the aqueous bath is 90 C.

10 to 95 C. and the flow thereof from the jet is sufficiently large to keep the temperature drop across said first feed wheel at a minimum.

5. In the process of stretching viscose yarn between two spaced positively driven feed wheels, the step which comprises applying a jet of hot aqueous liquid directly to the yarn on the first feed wheel and while the yarn is within a zone of 90 from the point it leaves said feed wheel to pass to the second feed wheel, the temperature of such aqueous liquid being such as to heat said yarn to a temperature of at least C.

6. In the process of stretching viscose yarn between two spaced positively driven feed wheels, the steps which comprise leading the yarn from the top of the first wheel to the second wheel, and applying a jet of hot aqueous liquid to the yarn while it is on the first wheel and within a zone of75 from'the point it leaves said first wheel to pass to said second wheel, the temperature of said aqueous liquid being such as to heat said yarn to a temperature of at least 75 C.

7. In the process of stretching viscose yarn between two spaced positively driven feed wheels, the steps which comprise leading the yarn from the downrunning side of the first wheel to the second wheel, and applying a jet of hot aqueous llquid to the yarn while it is on the first wheel and within a zone of45 to from the point it leaves said first wheel to pass to the second wheel, the'temperature of said aqueous liquid being such as to heat said yarn to a temperature of at least 75 C.

EMERSON A. TIPPET'IS.

REFERENCES CITED The following'references are UNITED STATES PATENTS Number Name Date 2,074,022 Oppenlaender Mar. 16, 1937 1,482,590 Thomas Feb. 5, 1924 1,882,612 Hufiord Oct. 11, 1932 2,209,841 McHugh July 30, 1940 1,977,611 Banigan Oct. 23, 1934 2,252,389 Vincke Aug. 12, 1941 2,265,984 Allen et a1 Dec. 16, 1941 2,174,576 Forrest Oct, 3, 1939 2,184,144 Huttinger Dec. 19, 1939 2,052,609 Dreyfus et al Sept. 1, 1936 2,309,072 Burkholder Jan. 19, 1943 2,346,696 Moritz Apr. 18, 1944 g FOREIGN PATENTS Number Country Date 187,396 Switzerland Sept. 21, 1935 

